| Abstract|| |
Introduction: Ependymomas are more common in the pediatric population, in whom they are commonly infratentorial. Extra axial location of a supratentorial ependymoma is extremely rare. Diagnosis: Radiologically these tumors are often misdiagnosed as meningioma or other extra axial lesions owing to their unusual location and lack of any pathognomonic features. Hence, histopathological examination becomes imperative for proper evaluation and an adequate diagnosis. Case: Herein we report a case of a supratentorial extra axial anaplastic ependymoma misdiagnosed as a metastatic tumor on radiological examination and mimicking meningioma intra operatively, located in the frontal and temporal region in a 20 year old man.
Keywords: Anaplastic, ependymoma, extra-axial, supratentorial
|How to cite this article:|
Uttam P, Hussain N. Extra-Axial supratentorial anaplastic ependymoma: Unusual location of an aggressive tumor, A case report. Indian J Pathol Microbiol 2022;65:668-70
|How to cite this URL:|
Uttam P, Hussain N. Extra-Axial supratentorial anaplastic ependymoma: Unusual location of an aggressive tumor, A case report. Indian J Pathol Microbiol [serial online] 2022 [cited 2022 Oct 1];65:668-70. Available from: https://www.ijpmonline.org/text.asp?2022/65/3/668/351600
| Introduction|| |
Ependymomas are glial tumors arising from the ependymal lining of the ventricular system or the central canal of the spinal cord. They comprise 2%–9% of all the intracranial tumors, being more common in the pediatric population. The majority of these lesions arise infratentorially with only one-third of cases being supratentorial., Approximately half of the supratentorial ependymomas arise from parenchyma, whereas the remaining cases are primarily intraventricular. Primary intracranial extra-axial ependymomas are very rare.
| Case Details|| |
A 20-year-old man presented with a complaint of headache and vomiting since 1 month with a single episode of seizure 20 days back. On neurological examination, no focal neurological deficit was noted. Clinical history revealed gross total removal of a supratentorial anaplastic ependymoma in the right frontal region 2 years back with subsequent conventional radiotherapy, at an outside center. CE-MRI showed a heterogeneously enhancing lesion measuring 65 × 55 mm in the right frontal lobe with disproportionate perifocal edema and mass effect in the form of partial effacement of adjacent lateral ventricle and subfalcine herniation, suggestive of recurrence. Another heterogeneously enhancing lesion measuring 25 mm × 21 mm was noted in the right temporal region with broad base toward dura, suggestive of extra-axial lesion, likely metastasis.
Patient underwent right frontotemporal craniotomy with tumor resection. Intra-operatively the temporal mass was extra-axial and well defined with blood supply from the dura. No obvious invasion into the parenchyma or continuity with the ventricular system noted. Intra-operative impression was that of a meningioma.
Microscopic examination showed a cellular tumor arranged in nodules and sheets with focal perivascular pseudorosettes, composed of round to oval cells with speckled chromatin, nuclear atypia and brisk mitosis (6-7/10HPF). Large areas of geographic and palisading necrosis and focal calcification was also noted [Figure 1]. No whorls or intranuclear pseudoinclusions suggestive of meningioma were noted. The tumor cells were strongly immunopositive for GFAP with perivascular accentuation. Perivascular dot like positivity for EMA was noted focally [Figure 2]. The tumor cells were immunonegative for pan CK ruling out metastatic carcinoma. MIB1 labeling index was 20-25%. L1CAM was positive, IDH1 negative and expression of ATRX was retained. IHC for OLIG 2, synaptophysin and NF were negative.
|Figure 1: Histopathologic examination of hematoxylin and eosin stained slides showed a cellular tumor arranged in nodules and sheets with delicate capillary blood vessels (×100) (a). Large areas of multifocal geographic and palisading necrosis and focal calcification was also noted (×100) (b). Perivascular pseudorosettes were note focally (×400) (c). The tumor was composed of round to oval cells with speckled chromatin, nuclear atypia and brisk mitosis (6-7/10HPF) (×400) (d)|
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|Figure 2: On immunohistochemistry, the tumor cells showed perivascular dot like positivity for EMA (×100) (a), strong immunopositivity for GFAP with perivascular accentuation (×100) (b) and high Ki67 (×100) (c), (×400) (d)|
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Based on these findings, a diagnosis of anaplastic ependymoma, WHO grade III was rendered.
| Discussion|| |
Ependymomas preferentially affect the pediatric population, in whom most are located infratentorially whereas tumors in adults have a propensity for development in supratentorial space. Approximately half of the supratentorial ependymomas arise from parenchyma, whereas the remaining cases are primarily intraventricular. Primary extra-axial ependymomas are very rare. The first case of intra-cranial extra-axial ependymoma was reported by Hanchey et al. in 1975. Since then 11 cases have been reported in the literature.
Most of the previously reported cases were seen in males with a mean age of 37.2 years. Patients with supratentorial tumors usually present with headache, nausea/vomiting, seizures and focal neurological deficit, in contrast to infratentorial tumors which present with signs and symptoms related to hydrocephalous. In the present case, patient is a 20-year-old man who presented with headache, vomiting and a single episode of seizure; however, no symptom suggestive of neurological deficit was seen.
The intracranial extra-axial tumors can grow up to large masses without producing any symptoms, as the typical symptoms of raised intracranial tension may appear late owing to extra-axial nature of these tumors. The mean duration of symptoms was 18.2 months in the previously reported cases. In our case the duration of symptoms was only 1 month; however, this was a case of recurrence in a previously operated case of supratentorial extra-axial anaplastic ependymoma.
The mechanism of oncogenesis in these cases is not well defined, although several hypotheses have been proposed. The most favored hypothesis proposes the origin of tumor from ectopic ependymal nests resulting from migration disorders during fetal development. Another possibility is the tumor development from subcortical, subependymal nests with extramedullary extension followed by necrosis or calcification of intra-axial component.
There are no pathognomonic features of intracranial extra-axial ependymomas on CT or MRI. They are generally iso- to hypointense on T1W images and iso- to hyperintense on T2W images with heterogenous enhancement after contrast due to calcification, necrosis, hemorrhage or cystic components. Similar features were noted in the present case. Due to atypical radiographic appearance and rarity of these tumors, they are often misdiagnosed as meningiomas.
Radiographically, extra-axial ependymomas can be difficult to differentiate from other dural-based lesions, as both can present with isointensity on T1- and T2- weighted images. The difference lies in their contrast enhancement, being in-homogenous in ependymomas unlike in meningiomas. Moreover, meningiomas often show dural tail sign which was not seen in the present case. MR spectroscopy may further help in differentiating these 2 entities. MR spectroscopy was not done in the present case. Other radiographic differentials include astrocytoma, supratentorial PNET, oligodendroglioma and ganglioglioma owing to the presence of cystic components, calcification, necrosis or hemorrhage. Our case was misdiagnosed as metastatic extra-axial lesion in right temporal lobe based on the presence of a broad base towards dura, and misdiagnosed as meningioma, as it was a brilliantly enhancing lesion with midline shift and subfalcine herniation.
A precise diagnosis is difficult preoperatively, owing to the absence of any pathognomonic radiographic findings and rarity of these tumors. Hence histological evaluation including immunohistochemistry is a must for optimal evaluation and diagnosis of these tumors.
Microscopically extra-axial ependymomas can present with unusual features, hence immunohistochemistry plays a very important role in evaluation. GFAP positivity helps in ruling out meningiomas and some other differentials like central neurocytoma which may resemble ependymoma morphologically. Oligodendrogliomas can show cytological features resembling ependymoma, but they can be ruled out based on the lack of EMA and perivascular pseudorosettes. L1CAM is a surrogate immunohistochemical marker of RELA-fusion positive supratentorial anaplastic ependymomas and are associated with poorer prognosis. IHC for L1CAM was positive in our case, thus conferring poorer prognosis.
Surgical resection remains the preferred management of these tumors, although the optimal treatment option including the use of radiotherapy is still not well defined owing to the rarity of IEAEs. Niazi et al. reviewed treatment options in supratentorial ependymomas in adults and concluded that all WHO grade III ependymomas require radiotherapy, while WHO grade II ependymomas can be managed by total resection without radiotherapy. Surgical removal extent of the tumor remains the most important prognostic factor. Recurrence has been reported in up to half of ependymoma patients by Mansur et al. In our case total surgical resection was followed by radiotherapy; however, the tumor recurred after 2 years.
| Conclusion|| |
Although extra-axial supratentorial ependymomas are extremely rare and have a wide spectrum of clinical and radiologic appearances, they should be considered in the differential diagnosis of extra-axial/dura-based lesions. Histological examination including immunohistochemistry is of paramount importance for proper evaluation and diagnosis of these tumors. Anaplastic tumors are prone to recurrence despite total resection and radiation therapy, hence a close follow-up is warranted.
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Department of Pathology and Lab Medicine, AIIMS Raipur, Gate No.5, GE Road, Tatibandh, Raipur, Chhattisgarh
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]